1. Field of the Invention
The present invention relates to an electronic circuit apparatus having a plurality of circuit boards (substrates) mounting a plurality of electronic parts thereon, and a motherboard joined to the circuit boards, and a method for assembling such an electronic circuit apparatus. More particularly, the present invention relates to an electronic circuit apparatus capable of efficiently dissipating heat generated by power devices, and requiring reduced work for assembling the same.
2. Related Art
In a conventional electronic circuit apparatus such as disclosed in JP-A-8-111575, semiconductor chips are mounted directly on a circuit board. Positioning pins attached to the circuit board are inserted in holes formed in a motherboard to connect the circuit board and the motherboard. The circuit board is made of a metal to dissipate heat generated by power devices.
If this apparatus has a plurality of circuit boards to achieve many functions, the motherboard needs an increased number of holes for receiving the positioning pins of the circuit boards. The holes reduce a space available for mounting electronic parts on the motherboard. Assembling the circuit boards with the motherboard requires increased man-hours. Furthermore, heat generated by the power devices on the circuit boards cannot be absorbed nor dissipated efficiently, because the circuit boards are provided individually with heat radiating fins (heat sinks).
It is therefore an object of the present invention to provide an electronic circuit apparatus capable of reducing space necessary for mounting on a motherboard a plurality of circuit boards mounted with a plurality of electronic parts thereon.
It is another object of the present invention to provide an electronic circuit apparatus capable of efficiently absorbing and dissipating heat generated by power devices mounted on a plurality of circuit boards.
It is a still another object of the present invention to reduce man-hours necessary for mounting a plurality of circuit boards on a motherboard.
In an electronic circuit apparatus according to one aspect of the present invention, a plurality of circuit boards having a plurality of electronic parts including heat-generative electronic parts thereon are joined to a heat radiating member. A motherboard is connected to the circuit boards. Heat generated by the heat-generative electronic parts on the circuit boards can efficiently be absorbed and radiated by the heat radiating member, and assembling the circuit board and the motherboard requires reduced man-hours. The electronic parts on the circuit boards and wiring patterns may be sealed simultaneously in a resin for packaging after bonding the circuit boards to the heat radiating member, thus requiring reduced man-hours for packaging.
In assembling the electronic circuit apparatus, the circuit boards are bonded to the heat radiating member, and then the heat radiating member is assembled on the motherboard.
In an electronic circuit apparatus according to another aspect of the present invention, a plurality of circuit boards mounted with a plurality of electronic parts are joined to a motherboard. A case has walls projecting toward the motherboard surrounds at least a part of a region in which the electronic parts are disposed. Thus, the efficiency of heat transfer from the electronic parts on the circuit boards to the case can be improved. The walls shield incoming noise to maintain the electronic circuits to be noise-resistant.